Engine control device

ABSTRACT

An engine control device for controlling an engine based on a vehicle operating state is provided, that includes a basic target torque determinator for setting a vehicle target acceleration based on an accelerator pedal operation and determining a basic target engine torque based on the vehicle target acceleration, a torque reduction demand determinator for determining whether an engine torque reduction is demanded based on the vehicle operating state other than the accelerator pedal operation, a torque reduction amount determinator for determining an engine torque reduction amount according to the operating state when the torque reduction is demanded, a final target torque determinator for determining as a final target torque an engine torque calculated by subtracting the torque reduction amount from the basic target torque when the torque reduction is demanded, and an engine controller for controlling the engine so as to output the final target torque.

BACKGROUND

The present invention relates to an engine control device, andparticularly to an engine control device which controls an engine basedon an operating state of a vehicle.

Conventionally, it is known that devices which control the behavior of avehicle to the safe side when the behavior of the vehicle becomesunstable due to a slip etc. (such as an antiskid brake system or ABS,etc.). Particularly, it is known that devices which detect a behaviorsuch as an understeering or an oversteering occurs on the vehicle duringcornering etc. of the vehicle, and give wheels a suitable decelerationso that the behavior is controlled.

Meanwhile, JP2011-088576A discloses a vehicle movement controller whichadjusts a deceleration during cornering to adjust a load applied tofront wheels which are steerable wheels so that a series of vehicleoperator's operations (breaking, steering-in, accelerating,steering-back, etc.) during cornering of a vehicle in a normal travelingstate are natural and stable, unlike the control described above for asafety improvement in the traveling state where the behavior of thevehicle becomes unstable.

Furthermore, JP2014-166014A discloses a behavior control device for avehicle which reduces a driving force of the vehicle according to ayaw-rate related amount corresponding to an operator's steeringoperation (e.g., yaw acceleration) to quickly decelerate the vehiclewhen the operator starts the steering operation so that a sufficientload is quickly applied to the front wheels which are steerable wheels.According to this behavior control device, since a frictional forcebetween the front wheels and the road surface increases, and a corneringforce of the front wheels increases by quickly applying the load to thefront wheels when the steering operation is activated, a turnability ofthe vehicle in an early stage of curve entry improves, and a response tothe steering-in operation improves. This achieves a vehicle behaviorjust as the operator intended.

It is known that a following travel control device which follows avehicle after a preceding vehicle as one of driving support devices inorder to ease operational burden of the operator. This following travelcontrol device controls a driving force in order to accelerate ordecelerate the vehicle so that a distance between two cars is keptconstant.

The vehicle behavior control device disclosed in JP2014-166014A controlsthe driving force of the vehicle to be quickly reduced according to asteering operation, in order to accurately achieve a vehicle behaviorwhich the operator intended.

The control of the driving force by the following travel control devicecompetes with the control of the driving force according to the steeringoperation by the vehicle behavior control device disclosed inJP2014-166014A. For this reason, the cornering force of the front wheelscannot fully be increased by quickly applying the load to the frontwheels unless the driving force control of the vehicle in response tothe operator's steering operation is appropriately performed. Therefore,a sufficient response cannot be secured for the steering-in operation.That is, the vehicle behavior which the operator intended cannotaccurately be achieved.

SUMMARY

The present invention is made in view of the above issues of theconventional technologies, and aims to provide an engine control devicewhich can control an engine so that a vehicle behavior which a vehicleoperator intended is accurately achieved, while appropriatelycooperating with other driving force controls.

According to one aspect of the present invention, an engine controldevice for controlling an engine based on an operating state of avehicle, is provided. The device includes a basic target torquedeterminator for setting a target acceleration of the vehicle based onan accelerator pedal operation and determining a basic target enginetorque based on the target acceleration of the vehicle, a torquereduction demand determinator for determining an existence of a demandto reduce an engine torque based on the operating state of the vehicleother than the accelerator pedal operation, a torque reduction amountdeterminator for determining an engine torque reduction amount accordingto the operating state when the torque reduction demand is determined toexist, a final target torque determinator for determining as a finaltarget torque an engine torque calculated by subtracting the torquereduction amount from the basic target torque when the torque reductiondemand is determined to exist, and an engine controller for controllingthe engine so as to output the final target torque.

With the above configuration, the final target torque determinatordetermines the final target torque based on the basic target torquedetermined based on the target acceleration of the vehicle, and thetorque reduction amount determined based on the operating state of thevehicle other than accelerator pedal operation. In addition, the enginecontroller controls the engine so as to output the final target torque.Thus, change in the torque reduction amount can be reflected in thefinal target torque, regardless of what kind of driving operation orcontrol of driving force is used for determining the basic targettorque. Therefore, a load can quickly be applied to front wheels bycontrolling the engine so that the torque reduction amount is obtainedwith a high response with respect to the operating state of the vehicleother than accelerator pedal operation, and a vehicle behavior which avehicle operator intended can accurately be achieved, whileappropriately cooperating with other driving force controls.

The engine control device may further include a following travel controldevice for controlling a traveling speed of the vehicle in order tofollow a preceding vehicle. When the torque reduction demand isdetermined to exist, even during the following control, the final targettorque determinator may determine as the final target torque the enginetorque calculated by subtracting the torque reduction amount from thebasic target torque for the following control.

With the above configuration, the basic target torque determinatordetermines the basic target torque based on the target accelerationdetermined by a vehicle speed control device such as the followingtravel control device, the final target torque determinator determinesthe final target torque based on the basic target torque and the torquereduction amount determined based on the operating state of the vehicleother than accelerator pedal operation, and the engine controllercontrols the engine so as to output the final target torque. Thus, thevehicle behavior which the operator intended can accurately be achievedeven when a vehicle speed control is performed by the following travelcontrol device, etc.

The torque reduction amount determinator may determine the torquereduction amount according to a steering operation of the vehicle.

With the above configuration, change in the torque reduction amount withtime which is determined based on the steering operation can bereflected in the change of the final target torque with time. Thus, theload can be applied to the front wheels by quickly adding decelerationaccording to the operator's steering operation to the vehicle, theresponse to the steering operation can be improved by quickly increasinga cornering force, and the engine can be controlled to accuratelyachieve the vehicle behavior which the operator intended whileappropriately cooperating with other driving force controls.

According to another aspect of the present invention, an engine controldevice for controlling an engine based on an operating state of avehicle, is provided. The device includes a basic target torquedeterminator for setting a target acceleration of the vehicle based onan accelerator pedal operation and determining a basic target enginetorque based on the target acceleration of the vehicle, a change rateacquirer for acquiring a rate of change of a steering operation of thevehicle, a target additional deceleration setter for increasing a targetadditional deceleration while a rate of the increase becomes less as thechange rate increases, a torque reduction amount determinator fordetermining an engine torque reduction amount according to the targetadditional deceleration when the torque reduction demand is determined,a final target torque determinator for determining as a final targettorque an engine torque calculated by subtracting the torque reductionamount from the basic target torque when the torque reduction demand isdetermined to exist, and an engine controller for controlling the engineso as to output the final target torque.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an outline configuration diagram of an engine system to whichan engine control device according to one embodiment of the presentinvention is applied.

FIG. 2 is a block diagram illustrating an electric configuration of theengine control device according to the embodiment of the presentinvention.

FIG. 3 is a flowchart of an engine control processing for controlling anengine by the engine control device according to the embodiment of thepresent invention.

FIG. 4 is a flowchart of a torque reduction amount determinationprocessing for determining a torque reduction amount by the enginecontrol device according to the embodiment of the present invention.

FIG. 5 is a map, illustrated in a form of a graph, in which a relationbetween a target additional deceleration and a steering speed determinedby the engine control device according to the embodiment of the presentinvention is illustrated.

FIG. 6 is an ignition advance map, illustrated in a form of a graph, inwhich a relation between an ignition timing and an indicated torque isdefined according to various air amounts and various engine speeds.

FIG. 7 illustrates a diagram and graphs of changes in parameters withtime during the engine control by the engine control device when avehicle equipped with the engine control device according to theembodiment of the present invention turns, where a part (a) is a planview schematically illustrating a vehicle which makes a turn to theright, a part (b) is a graph illustrating a change in a steering angleof the vehicle which makes a turn to the right as illustrated in thepart (a), a part (c) is a graph illustrating a change in a steeringspeed of the vehicle which makes a turn to the right as illustrated inthe part (b), a part (d) is a graph illustrating a change in anadditional deceleration which is determined based on the steering speedillustrated in the part (c), a part (e) is a graph illustrating a changein a torque reduction amount which is determined based on the additionaldeceleration illustrated in the part (d), a part (f) is a graphillustrating a change in a basic target torque before and after asmoothing by a torque change filter, a part (g) is a graph illustratinga change in a final target torque which is determined based on the basictarget torque and the torque reduction amount, a part (h) is a graphillustrating changes in the target air amount which is determined basedon the final target torque and an actual air amount, a part (i) is agraph illustrating a torque reduction ignition timing which isdetermined based on the final target torque and the actual air amount,with respect to a basic ignition timing, and a part (j) is a graphillustrating a change in a yaw rate (actual yaw rate) which is caused inthe vehicle when the control of the intake air amount and the ignitiontiming is performed as illustrated in the parts (h) and (i), and achange in an actual yaw rate when the control of the air amount and theignition timing based on the torque reduction amount which is determinedby the torque reduction amount determinator is not performed.

DETAILED DESCRIPTION

Hereinafter, an engine control device according to one embodiment of thepresent invention is described with reference to the accompanyingdrawings.

First, an engine system to which the engine control device according tothe embodiment of the present invention is applied is described withreference to FIGS. 1 and 2. FIG. 1 is an outline configuration diagramof the engine system to which the engine control device according tothis embodiment of the present invention is applied, and FIG. 2 is ablock diagram illustrating an electric configuration of the enginecontrol device according to this embodiment of the present invention.

As illustrated in FIGS. 1 and 2, the engine system 100 includes,primarily, an intake passage 1 through which intake air introduced fromoutside passes, the engine 10 (particularly, a gasoline engine) whichcombusts a mixture gas of the air supplied from the intake passage 1 andfuel supplied from a fuel injector 13 (described later) to generate adriving force for a vehicle, an exhaust passage 25 which dischargesexhaust gas generated by combustion inside the engine 10, sensors 30-40which detect various kinds of states regarding an engine system 100, anda PCM 50 (engine control device) which controls the entire engine system100. It will be appreciated that the PCM 50 is a hardware device thatincludes a processor configured to execute various software programsstored in non-volatile memory of the PCM 50, including those softwareprograms depicted at 51-59 in FIG. 2.

Provided in the intake passage 1 are, sequentially from upstream, an aircleaner 3 which purifies the intake air introduced from outside, athrottle valve 5 which adjusts an amount of passing intake air (intakeair amount), and a surge tank 7 which temporarily stores the intake airsupplied to the engine 10.

The engine 10 primarily includes an intake valve 12 which introduces theintake air supplied from the intake passage 1 into a combustion chamber11, the fuel injector 13 which injects the fuel toward the combustionchamber 11, an ignition plug 14 which ignites the mixture gas of theintake air and the fuel which are supplied into the combustion chamber11, a piston 15 which reciprocates by combustion of the mixture gasinside the combustion chamber 11, a crankshaft 16 which rotates by thereciprocating motion of the piston 15, and an exhaust valve 17 whichdischarges the exhaust gas generated by the combustion of the mixturegas inside the combustion chamber 11 to the exhaust passage 25.

Moreover, the engine 10 is configured such that a variable intake valvemechanism 18 and a variable exhaust valve mechanism 19 as a variablevalve timing mechanism vary operating timings of the intake valve 12 andthe exhaust valve 17 (corresponding to valve phases). The variableintake valve mechanism 18 and the variable exhaust valve mechanism 19may adopt various types of well-known mechanisms. For example, theoperating timings of the intake valve 12 and the exhaust valve 17 may bevaried using the electromagnetic or hydraulic mechanisms.

Primarily provided in the exhaust passage 25 are exhaust purificationcatalysts 26 a and 26 b having a purification function of exhaust gas,such as a NO_(x) catalyst, a three-way catalyst, or an oxidationcatalyst. Below, if the exhaust purification catalysts 26 a and 26 b areused without distinguishing one from the other, they are comprehensivelyreferred to as “the exhaust purification catalyst 26.”

The engine system 100 is also provided with the sensors 30-40 whichdetect various kinds of states regarding the engine system 100. Thesesensors 30-40 are particularly as follows. The accelerator openingsensor 30 detects an accelerator opening which is an opening of anaccelerator pedal (corresponding to a stepping-on amount of theaccelerator pedal by a vehicle operator). The airflow sensor 31 detectsthe intake air amount corresponding to a flow rate of the intake airwhich passes through the intake passage 1. The throttle opening sensor32 detects a throttle opening which is a valve opening of the throttlevalve 5. The pressure sensor 33 detects an intake manifold pressurecorresponding to a pressure of the intake air supplied to the engine 10.The crank angle sensor 34 detects a crank angle of the crankshaft 16.The water temperature sensor 35 detects a water temperature which is atemperature of coolant for cooling the engine 10. The temperature sensor36 detects a cylinder temperature which is a temperature inside thecylinder of the engine 10. The cam angle sensors 37 and 38 detectoperating timings including valve-close timings of the intake valve 12and the exhaust valve 17, respectively. The vehicle speed sensor 39detects a speed of the vehicle (vehicle speed). The steering anglesensor 40 detects a rotation angle of a steering wheel. Note that thesevarious sensors 30-40 respectively output detection signals S130-S140corresponding to detected parameters to the PCM 50.

The PCM 50 controls components of the engine system 100 based on thedetection signals S130-S140 inputted from the various sensors 30-40.Particularly as illustrated in FIG. 2, the PCM 50 supplies the controlsignal S105 to the throttle valve 5 to control the open and closetimings, and the throttle opening of the throttle valve 5, supplies thecontrol signal S113 to the fuel injector 13 to control a fuel injectionamount and a fuel injection timing, supplies the control signal S114 tothe ignition plug 14 to control the ignition timing, and supplies thecontrol signals S118 and S119 to the variable intake valve mechanism 18and the variable exhaust valve mechanism 19 to control the operatingtimings of the intake valve 12 and the exhaust valve 17, respectively.

A control signal S160 corresponding to a target acceleration (includingnegative acceleration or deceleration) to follow the vehicle after apreceding vehicle is also inputted into the PCM 50 from a followingtravel control device 60 (a vehicle speed control device). For example,the following travel control device 60 detects a distance between twocars (the vehicle and the preceding vehicle which travels ahead of thevehicle), for example by a millimeter wave radar or a near-infraredlaser radar, and sets the target acceleration for controlling thetraveling speed so that the distance between the two cars is maintainedat a given distance. If there is no preceding vehicle, the followingtravel control device 60 sets the target acceleration required in orderto maintain the vehicle at a given traveling speed. The following travelcontrol device 60 then outputs the control signal S160 of the targetacceleration setting to the PCM 50.

The PCM 50 includes a basic target torque determinator 51 whichdetermines a basic target torque based on the operating state of thevehicle including the accelerator pedal operation, a torque reductionamount determinator 53 which determines a torque reduction amount basedon the operating state of the vehicle which does not include theaccelerator pedal operation, a final target torque determinator 55 whichdetermines a final target torque based on the basic target torque andthe torque reduction amount, a torque change filter 57 which smoothes achange in the final target torque with time, and an engine controller 59which controls the engine 10 so that the engine 10 outputs the finaltarget torque.

Each component of the PCM 50 is comprised of a computer provided with aCPU, various kinds of programs to be interpreted and executed on the CPU(including primary control programs, such as OS and application programswhich are activated on the OS and achieve specific functions), and aninternal memory, such as a ROM and a RAM for storing the programs andvarious kinds of data.

Next, processings performed by the engine control device are describedwith reference to FIGS. 3 to 6.

FIG. 3 is a flowchart of an engine control processing for controllingthe engine 10 by the engine control device according to this embodimentof the present invention, FIG. 4 is a flowchart of a torque reductionamount determination processing for determining the torque reductionamount by the engine control device according to this embodiment of thepresent invention, FIG. 5 is a map in which a relation between a targetadditional deceleration and a steering speed determined by the enginecontrol device according to this embodiment of the present invention isillustrated, and FIG. 6 is an ignition advance map in which the relationbetween the ignition timing and an indicated torque is defined accordingto various air amounts and various engine speeds.

The engine control processing of FIG. 3 is activated when an ignitionswitch of the vehicle is turned ON, and power is supplied to the enginecontrol device. The engine control processing is repeatedly executed.

When the engine control processing is activated, as illustrated in FIG.3, the PCM 50 acquires the operating state of the vehicle at Step S1.For example, the PCM 50 acquires, as the operating state, theaccelerator opening detected by the accelerator opening sensor 30, thevehicle speed detected by the vehicle speed sensor 39, the steeringangle detected by the steering angle sensor 40, the detection signalsS130-S140 outputted from the various sensors 30-40 described aboveincluding a gear position currently set at a transmission of thevehicle, and the control signal S160 of the target accelerationoutputted from the following travel control device 60, etc.

Next, at Step S2, the basic target torque determinator 51 of the PCM 50sets the target acceleration based on the operating state of the vehicleincluding the accelerator pedal operation acquired at Step S1. Forexample, when the following travel control is not performed by thefollowing travel control device 60, the basic target torque determinator51 selects an acceleration characteristic map corresponding to thecurrent vehicle speed and gear position from acceleration characteristicmaps defined for various vehicle speeds and gear positions (they arecreated beforehand and stored in the memory etc.), and determines thetarget acceleration corresponding to the current accelerator openingwhile referring to the selected acceleration characteristic map. Whenthe following travel control is performed by the following travelcontrol device 60, the basic target torque determinator 51 determines atarget acceleration specified by the control signal S160 inputted fromthe following travel control device 60 as the target acceleration.

Next, at Step S3, the basic target torque determinator 51 determines thebasic target torque of the engine 10 for achieving the targetacceleration determined at Step S2. In that case, the basic targettorque determinator 51 determines the basic target torque within atorque range which is outputable by the engine 10, based on the vehiclespeed, the gear position, a road surface slope, a road surface frictioncoefficient, etc. at this time point.

Next, at Step S4, the torque change filter 57 smoothes the change in thebasic target torque with time determined at Step S3. The smoothing maybe achieved by various known techniques, such as limiting a rate ofchange in the basic target torque to below a threshold, and calculatinga moving average of the change in the basic target torque with time.

In parallel to the processings at Steps S2-S4, the torque reductionamount determinator 53 performs the torque reduction amountdetermination processing at Step S5 for determining the torque reductionamount based on the operating state of the vehicle other than theaccelerator pedal operation. This torque reduction amount determinationprocessing is described with reference to FIG. 4.

As illustrated in FIG. 4, once the torque reduction amount determinationprocessing is activated, the torque reduction amount determinator 53determines at Step S21 whether an absolute value of the steering angleacquired at Step S1 is increasing. As a result, if the absolute value ofthe steering angle is increasing, the processing then transits to StepS22 where the torque reduction amount determinator 53 calculates thesteering speed based on the steering angle acquired at Step S1.

Next, at Step S23, the torque reduction amount determinator 53determines whether the absolute value of the steering speed isdecreasing.

As a result, if the absolute value of the steering speed is notdecreasing (i.e., if the absolute value of the steering speed isincreasing or not changed), the processing then transits to Step S24where the torque reduction amount determinator 53 acquires a targetadditional deceleration based on the steering speed. This targetadditional deceleration is a deceleration to be added to the vehicleaccording to the steering operation in order to accurately achieve thevehicle behavior which the operator intended.

For example, the torque reduction amount determinator 53 acquires thetarget additional deceleration corresponding to the steering speedcalculated at Step S22 based on the relation between the targetadditional deceleration and the steering speed which are illustrated inthe map of FIG. 5.

Note that the horizontal axis in FIG. 5 indicates the steering speed,and the vertical axis indicates the target additional deceleration. Asillustrated in FIG. 5, if the steering speed is below a threshold Ts(e.g., 10 deg/s), a corresponding target additional deceleration is zero(0). That is, if the steering speed is below the threshold Ts, thecontrol for adding the deceleration to the vehicle according to thesteering operation is not performed.

On the other hand, if the steering speed is above the threshold Ts, thetarget additional deceleration corresponding to the steering speedgradually approaches a given upper limit D_(max) (e.g., 1 m/s²) as thesteering speed increases. That is, the target additional decelerationincreases as the steering speed increases, but a rate of the increasebecomes less.

Next, at Step S25, the torque reduction amount determinator 53determines the additional deceleration in the current processing withina range where the increasing rate of the additional deceleration becomesbelow a threshold Rmax (e.g., 0.5 m/s³).

For example, if the increasing rate from the additional decelerationdetermined in the previous processing to the target additionaldeceleration determined at Step S24 in the current processing is belowRmax, the torque reduction amount determinator 53 determines the targetadditional deceleration determined at Step S24 as the additionaldeceleration in the current processing

On the other hand, if the rate of change from the additionaldeceleration determined in the previous processing to the targetadditional deceleration determined at Step S24 in the current processingis above Rmax, the torque reduction amount determinator 53 determines avalue which is obtained by increasing the additional decelerationdetermined in the previous processing by the increasing rate Rmax for aperiod between the previous processing and the current processing, asthe additional deceleration in the current processing.

At Step S23, if the absolute value of the steering speed is decreasing,the processing then transits to Step S26 where the torque reductionamount determinator 53 determines the additional deceleration determinedin the previous processing as the additional deceleration in thisprocessing. That is, if the absolute value of the steering speed isdecreasing, the additional deceleration when the steering speed is themaximum (i.e., the maximum value of the additional deceleration) ismaintained.

At Step S21, if the absolute value of the steering angle is notincreasing (i.e., constant or decreasing), the processing then transitsto Step S27 where the torque reduction amount determinator 53 acquires adecreasing amount in the current processing from the additionaldeceleration determined in the previous processing (a decelerationreduction amount). This deceleration reduction amount may be calculatedbased on a fixed rate of decrease which is stored beforehand in thememory etc. (e.g., 0.3 m/s³). Alternatively, the deceleration reductionamount may be calculated based on a rate of decrease determinedaccording to the operating state of the vehicle acquired at Step S1and/or the steering speed calculated at Step S22.

At Step S28, the torque reduction amount determinator 53 determines theadditional deceleration in the current processing by subtracting thedeceleration reduction amount acquired at Step S27 from the additionaldeceleration determined in the previous processing.

After Step S25, S26 or S28, the torque reduction amount determinator 53determines at Step S29 the torque reduction amount based on the currentadditional deceleration determined at Step S25, S26 or S28. For example,the torque reduction amount determinator 53 determines the torquereduction amount which is needed in order to achieve the currentadditional deceleration based on the current vehicle speed and gearposition, road surface slope, etc. which are acquired at Step S1. AfterStep S29, the torque reduction amount determinator 53 ends the torquereduction amount determination processing, and returns to the mainroutine.

Returning to FIG. 3, after performing the processings at Steps S2-S4 andthe torque reduction amount determination processing at Step S5, thefinal target torque determinator 55 determines at Step S6 the finaltarget torque by subtracting the torque reduction amount determined inthe torque reduction amount determination processing at Step S5 from thebasic target torque after the smoothing at Step S4.

Next, at Step S7, the engine controller 59 determines the target airamount and a target equivalence ratio so that the engine 10 outputs thefinal target torque determined at Step S6. Here, the “air amount” is anamount of air introduced into the combustion chamber 11 of the engine10. Note that a filling efficiency which is obtained by converting theair amount into a no-dimensional value may instead be used.

For example, the engine controller 59 calculates a target indicatedtorque which is obtained from the final target torque in considerationof a torque loss caused by a friction loss and/or a pumping loss,calculates a target generated heat amount required for generating thetarget indicated torque, and determines the target air amount based onthe target generated heat amount and the target equivalence ratio.

Next, at Step S8, the engine controller 59 determines the valve openingof the throttle valve 5, and the open and close timings of the intakevalve 12 through the variable intake valve mechanism 18 in considerationof the air amount detected by the airflow sensor 31 so that air of thetarget air amount determined at Step S7 is introduced into the engine10.

Next, at Step S9, the engine controller 59 controls the throttle valve 5and the variable intake valve mechanism 18 based on the throttleopening, and the open and close timings of the intake valve 12determined at Step S8, and controls the fuel injector 13 based on thetarget equivalence ratio determined at Step S7 and an actual air amountestimated based on the detection signal S131 of the airflow sensor 31,etc.

Next, at Step S10, the engine controller 59 determines the existence ofa demand of the torque reduction based on the operating state of thevehicle other than accelerator pedal operation. For example, the enginecontroller 59 determines that the demand of the torque reduction existsif the torque reduction amount determined in the torque reduction amountdetermination processing at Step S5 is above zero.

As a result, if there is the demand of the torque reduction, theprocessing then transits to Step S11 where the engine controller 59determines a torque reduction ignition timing so that the engine 10outputs the final target torque, based on the final target torquedetermined at Step S6, and the actual air amount actually introducedinto the combustion chamber 11 by the control of the throttle valve 5and the variable intake valve mechanism 18 at Step S9.

For example, the engine controller 59 estimates the actual air amountbased on the detection signal S131 of the airflow sensor 31, etc. Then,the engine controller 59 selects an ignition advance map correspondingto the actual air amount which is estimated and the engine speed fromthe ignition advance maps (created beforehand and stored in the memoryetc.) which define the relation between the ignition timing and theindicated torque for various air amounts and various engine speeds, anddetermines as torque reduction ignition timing, the ignition timingcorresponding to the target indicated torque which is calculated at StepS7 while referring to the selected ignition advance map.

As illustrated in FIG. 6, the ignition advance map has a horizontal axisas the ignition timing and a vertical axis as the indicated torque, andis expressed by an upwardly convex curve where the indicated torquedecreases as the ignition timing is advanced or retarded, having a localmaximum of the indicated torque when the ignition timing is at MBT(Minimum Advance for Best Torque).

If the response of the actual air amount is delayed with respect to thereduction of the target air amount corresponding to the torque reductiondemand, and the actual air amount is excessive against the target airamount, the indicated torque (illustrated by a solid line in FIG. 6) atMBT_(R) in the ignition advance map corresponding to the actual airamount is larger than the indicated torque (illustrated by a dotted linein FIG. 6) at MBT_(S) in the ignition advance map corresponding to thetarget air amount. In other words, an ignition timing Ig_(R) (i.e., atorque reduction ignition timing) corresponding to a target indicatedtorque Tr in the ignition advance map corresponding to the actual airamount is retarded from an ignition timing Ig_(S) corresponding to thetarget indicated torque Tr in the ignition advance map corresponding tothe target air amount. The torque reduction ignition timing is shiftedto the retard side as the actual air amount becomes more excessiveagainst the target air amount.

Next, at Step S12, the engine controller 59 controls the ignition plug14 so that ignition is performed at the torque reduction ignition timingdetermined at Step S11.

At Step S10, if there is no demand of the torque reduction, theprocessing then transits to Step S13 where the engine controller 59controls the ignition plug 14 so that ignition is performed at anignition timing (i.e., a basic ignition timing) with the most sufficientcombustion efficiency corresponding to the actual air amount which isactually introduced into the combustion chamber 11 by the control of thethrottle valve 5 and the variable intake valve mechanism 18 at Step S9.

For example, the engine controller 59 selects one of the ignitiontimings on the retard side as the basic ignition timing, from MBT in theignition advance map corresponding to the actual air amount and enginespeed, and a knock critical point ignition timing corresponding to theactual air amount and engine speed, and controls the ignition plug 14based on the selected ignition timing.

After Step S12 or S13, the PCM 50 ends the engine control processing.

Next, operation of the engine control device according to thisembodiment of the present invention is described with reference to FIG.7, which illustrates a diagram and graphs of changes in parameters withtime during the engine control by the engine control device when thevehicle carrying the engine control device according to this embodimentof the present invention turns.

A part (a) of FIG. 7 is a plan view schematically illustrating thevehicle which makes a turn to the right. As illustrated in the part (a),the vehicle starts a turn to the right from a position A, and thencontinues the right turn at a fixed steering angle from a position B toa position C.

A part (b) of FIG. 7 is a graph illustrating a change in the steeringangle of the vehicle which makes the turn to the right as illustrated inthe part (a). In the part (b), the horizontal axis indicates time andthe vertical axis indicates the steering angle.

As illustrated in the part (b), a rightward steering is started at theposition A, a rightward steering angle increases gradually by performingan additional steering operation, and the rightward steering anglebecomes the maximum at the position B. The steering angle is then keptconstant at the position C (steering maintained).

A part (c) of FIG. 7 is a graph illustrating a change in a steeringspeed of the vehicle which makes the turn to the right as illustrated inthe part (b). In the part (c), the horizontal axis indicates time andthe vertical axis indicates the steering speed.

The steering speed of the vehicle is expressed by a derivative of thesteering angle of the vehicle with respect to time. That is, asillustrated in the part (c), when the rightward steering is started atthe position A, a rightward steering speed occurs, and the steeringspeed is kept almost constant between the position A and the position B.Then, the rightward steering speed decreases, and the steering speedbecomes zero when the rightward steering angle reaches the maximum atthe position B. Furthermore, the steering speed remains at zero whilethe rightward steering angle is maintained from the position B to theposition C.

A part (d) of FIG. 7 is a graph illustrating a change in the additionaldeceleration which is determined based on the steering speed illustratedin the part (c). In the part (d), the horizontal axis indicates time andthe vertical axis indicates the additional deceleration. Moreover, thesolid line in the part (d) illustrates a change in the additionaldeceleration determined in the torque reduction amount determinationprocessing of FIG. 4, and a dotted chain line illustrates a change inthe target additional deceleration based on steering speed. The targetadditional deceleration illustrated by a one-point chain line begins toincrease from the position A, is kept almost constant between theposition A and the position B, and then decreases to reach zero at theposition B, similar to the change in the steering speed illustrated inthe part (c).

As described with reference to FIG. 4, the torque reduction amountdeterminator 53 acquires the target additional deceleration based on thesteering speed at Step S24 if the absolute value of the steering speedis not decreasing at Step S23 (i.e., if the absolute value of thesteering speed is increasing or the absolute value of the steering speedis not changing). Then, at Step S25, the torque reduction amountdeterminator 53 determines the additional deceleration in eachprocessing cycle within a range where an increasing rate of theadditional deceleration becomes below the threshold Rmax.

The part (d) of FIG. 7 illustrates a case where the increasing rate ofthe target additional deceleration which starts increasing from theposition A exceeds the threshold Rmax. In that case, the torquereduction amount determinator 53 increases the additional decelerationso that the increasing rate equals to Rmax (i.e., a less increasing ratethan the target additional deceleration illustrated by the one-pointchain line). Moreover, if the target additional deceleration is keptalmost constant between the position A and the position B, the torquereduction amount determinator 53 determines that the additiondecelerating equals to the target additional deceleration.

Moreover, as described above, if the absolute value of the steeringspeed is decreasing at Step S23 in FIG. 4, the torque reduction amountdeterminator 53 maintains the additional deceleration of the maximumsteering speed. In the part (d) of FIG. 7, if the steering speed isdecreasing toward the position B, the target additional decelerationillustrated by the one-point chain line also decreases accordingly, butthe additional deceleration illustrated by the solid line maintains itsmaximum value until the position B.

Furthermore, as described above, at Step S21 in FIG. 4, if the absolutevalue of the steering angle is constant or decreasing, the torquereduction amount determinator 53 acquires the deceleration reductionamount at Step S27, and then decreases the additional deceleration bythe deceleration reduction amount. As illustrated in the part (d), thetorque reduction amount determinator 53 decreases the additionaldeceleration so that the decreasing rate of the additional decelerationbecomes gradually smaller (i.e., so that the slope of the solid linewhich illustrates the change in the additional deceleration becomesgradually gentler or less steep.)

A part (e) of FIG. 7 is a graph illustrating a change in the torquereduction amount which is determined based on the additionaldeceleration illustrated in the part (d). In the part (e), thehorizontal axis indicates time and the vertical axis indicates thetorque reduction amount.

As described above, the torque reduction amount determinator 53determines the torque reduction amount which is needed for achieving theadditional deceleration based on parameters, such as the current vehiclespeed, gear position, and road surface slope. Therefore, if theseparameters are constant, the torque reduction amount is determined so asto change similar to the change in the additional decelerationillustrated in the part (d).

A part (f) of FIG. 7 is a graph illustrating a change in the basictarget torque before and after a smoothing by the torque change filter57. In the part (f), the horizontal axis indicates time and the verticalaxis indicates the torque. Moreover, in the part (f), a dotted lineillustrates the basic target torque before smoothing by the torquechange filter 57, and a solid line illustrates the basic target torqueafter the smoothing by the torque change filter 57.

The basic target torque determined such as to achieve the targetacceleration determined based on the accelerator opening, speed, gearposition, etc. may have a steep change due to various kinds ofdisturbances, noises, etc., as illustrated by the dotted line in thepart (f). Since the basic target torque is smoothed by the torque changefilter 57, a steep change is controlled as illustrated by the solid linein the part (f) and, thus a rapid acceleration and/or deceleration ofthe vehicle is controlled.

A part (g) of FIG. 7 is a graph illustrating a change in the finaltarget torque which is determined based on the basic target torque andthe torque reduction amount. In the part (g), the horizontal axisindicates time and the vertical axis indicates the torque. Moreover, inthe part (g), a dotted line illustrates the basic target torque afterthe smoothing illustrated in the part (f), and a solid line illustratesthe final target torque.

As described with reference to FIG. 3, the final target torquedeterminator 55 determines the final target torque by subtracting thetorque reduction amount determined in the torque reduction amountdetermination processing at Step S5 from the basic target torque afterthe smoothing at Step S4.

That is, when the following travel control is performed by the followingtravel control device 60, the final target torque is determined bysubtracting the torque reduction amount from the basic target torqueeven if the basic target torque is determined in order to achieve thetarget acceleration specified by the following travel control device 60.Thus, as illustrated by the solid line in the part (g), the torquereduction amount is reflected in the final target torque as it is,without being influenced by the following travel control.

A part (h) of FIG. 7 is a graph illustrating changes in the target airamount which is determined based on the final target torque and theactual air amount. In the part (h), the horizontal axis indicates timeand the vertical axis indicates the air amount. Moreover, a one-pointchain line in the part (h) illustrates the target air amountcorresponding to the final target torque illustrated in the part (g),and a solid line illustrates the actual air amount actually introducedinto the combustion chamber 11 by the control of the throttle valve 5and the variable intake valve mechanism 18 according to the final targettorque.

As illustrated in the part (h), the target air amount changessynchronizing with the change in the final target torque with time, buta delay occurs in the response of the actual air amount against thechange in the target air amount. That is, the actual air amount becomesexcessive when the target air amount decreases, and the actual airamount is insufficient when the target air amount increases.

A part (i) of FIG. 7 is a graph illustrating the torque reductionignition timing which is determined based on the final target torque andthe actual air amount, with respect to the basic ignition timing. In thepart (i), the horizontal axis indicates time and the vertical axisindicates the ignition timing with respect to the basic ignition timing(advancing is positive and retarding is negative).

As illustrated in the part (h), since a delay occurs in the response ofthe actual air amount and the actual air amount becomes excessiveagainst the target air amount when the target air amount decreasesaccording to the decrease of the final target torque, the decrease ofthe final target torque cannot be achieved by the decreasing amount ofthe actual air amount alone. Thus, the decrease of the final targettorque is achieved by retarding the torque reduction ignition timingfrom the basic ignition timing based on the final target torque and theactual air amount.

A part (j) of FIG. 7 is a graph illustrating a change in a yaw rate(actual yaw rate) which is caused in the vehicle when the engine 10 iscontrolled so as to achieve the final target torque illustrated in thepart (g), and a change in an actual yaw rate when the controlcorresponding to the torque reduction amount illustrated in the part (e)is not performed (i.e., when the engine 10 is controlled so as toachieve the basic target torque after the smoothing illustrated by thedotted line in the part (g)), in the vehicle where the steering asillustrated in the part (b) is performed. In the part (j), thehorizontal axis indicates time and the vertical axis indicates the yawrate. Moreover, a solid line in the part (j) illustrates a change in theactual yaw rate when the engine 10 is controlled so as to achieve thefinal target torque, and a dotted line illustrates a change in theactual yaw rate when the control corresponding to the torque reductionamount is not performed.

A rightward steering is started at the position A, and when the torquereduction amount is increased as illustrated in the part (e) accordingto an increase of the rightward steering speed, a load to the frontwheels which are steerable wheels of the vehicle increases. As a result,since the frictional force between the front wheels and the road surfaceincreases and the cornering force of the front wheels increases, aturnability of the vehicle improves. That is, between the position A andthe positions B as illustrated in the part (j), the yaw rate in theclockwise direction (CW) generated on the vehicle becomes larger whenthe engine 10 is controlled so as to achieve the final target torquereflecting the torque reduction amount (solid line), than when thecontrol corresponding to the torque reduction amount is not performed(dotted line).

Moreover, as illustrated in the parts (d) and (e), the target additionaldeceleration also decreases when the steering speed decreases toward theposition B, but since the maximum torque reduction amount is maintained,the load applied to the front wheels is maintained while the steering-inis continued and, thus, the turnability of the vehicle is maintained.

Furthermore, when the absolute value of the steering angle is constantat the position C from the position B, since the torque reduction amountis smoothly decreased, the load applied to the front wheels is graduallyreduced in response to the end of the steering-in, and the output torqueof the engine 10 is recovered while stabilizing the vehicle body bydecreasing the cornering force of the front wheels.

Next, further modifications of this embodiment of the present inventionare described.

Although in the above embodiment, the torque reduction amountdeterminator 53 acquires the target additional deceleration based on thesteering speed, and determines the torque reduction amount based on thetarget additional deceleration. Alternatively, the torque reductionamount may be determined based on the operating state of the vehicleother than accelerator pedal operation, such as the steering angle,and/or the yaw rate.

For example, the torque reduction amount determinator 53 may calculate atarget yaw acceleration to be generated on the vehicle based on thetarget yaw rate calculated based on the steering angle and the vehiclespeed, or the yaw rate inputted from the yaw rate sensor, and acquirethe target additional deceleration based on the target yaw accelerationto determine the torque reduction amount. Alternatively, the lateralacceleration generated with revolution of the vehicle is detected by anacceleration sensor, and the torque reduction amount may be determinedbased on this lateral acceleration. Alternatively, the torque reductionamount determinator 53 may determine the torque reduction amount basedon a demand different from the target additional deceleration (e.g., atorque required for cancelling vibration of a power train duringacceleration or deceleration).

Moreover, in the above embodiment, the following travel control device60 inputs the control signal S160 corresponding to the targetacceleration for following the vehicle after the preceding vehicle intothe PCM 50. Along with the control signal S160 from the following travelcontrol device 60, a control signal may also be inputted from thevehicle speed control device which controls the engine 10 so as tomaintain a given vehicle speed. Also in this case, since the finaltarget torque is determined by subtracting the torque reduction amountfrom the basic target torque, the torque reduction amount is reflectedin the final target torque as it is, without being influenced by thevehicle speed control.

Next, effects of the engine control device according to the embodimentof the present invention and the modifications of the embodiment of thepresent invention described above are described.

First, the engine controller 59 determines the target air amount so thatthe engine 10 outputs the final target torque, controls the throttlevalve 5 and the variable intake valve mechanism 18 so as to achieve thetarget air amount, and retards the ignition timing of the ignition plug14 more as the actual air amount becomes more excessive against thetarget air amount. Thus, even if the actual air amount becomes excessiveagainst the target air amount due to the delay in response of the actualair amount when the target air amount decreases according to thedecrease of the final target torque, and the decrease of the finaltarget torque cannot be achieved by the decreasing of the actual airamount alone, the output torque can be reduced by retarding the ignitiontiming. Therefore, the decrease of the final target torque according tothe change in the torque reduction amount can be achieved. Therefore,the engine 10 can be controlled so that the torque reduction amount isobtained with a high response with respect to the operating state of thevehicle other than the accelerator pedal operation, the load can bequickly applied to the front wheels, and the vehicle behavior which theoperator intended can accurately be achieved.

Particularly, if the torque reduction amount is above zero, the enginecontroller 59 controls the ignition system so that ignition is performedat an ignition timing for achieving the final target torque under theoperating state of the engine including the actual air amount and theengine speed at the time point. If the torque reduction amount is zero,the engine controller 59 controls the ignition system so that ignitionis performed at the given basic ignition timing for the operating stateof the engine including the actual air amount and the engine speed atthe time point. Thus, only when there is a torque reduction demandaccording to the operating state of the vehicle other than acceleratorpedal operation, the ignition timing can be retarded according to thefinal target torque and the actual air amount. Therefore, a degradationof the fuel consumption due to retarding of the ignition timing can beminimized, while accurately achieving the vehicle behavior which theoperator intended.

Moreover, since the torque reduction amount determinator 53 determinesthe torque reduction amount according to the steering operation of thevehicle, the change in the torque reduction amount with time which isdetermined based on the steering operation can be reflected in thechange in the final target torque with time. Accordingly, the load canbe applied to the front wheels by quickly adding the decelerationaccording to the operator's steering operation to the vehicle, theresponse to the steering operation can be improved by quickly increasingthe cornering force, and the engine 10 can be controlled to accuratelyachieve the vehicle behavior which the operator intended.

Moreover, the final target torque determinator 55 determines the finaltarget torque based on the basic target torque determined based on thetarget acceleration of the vehicle, and the torque reduction amountdetermined based on the operating state of the vehicle other thanaccelerator pedal operation. In addition, the engine controller 59controls the engine 10 so as to output the final target torque. Thus,the change in the torque reduction amount can be reflected in the finaltarget torque, regardless of what kind of driving operation or controlis used for determining the basic target torque. Therefore, the load canquickly be applied to the front wheels by controlling the engine 10 sothat the torque reduction amount is obtained with a high response withrespect to the operating state of the vehicle other than acceleratorpedal operation, and the vehicle behavior which the operator intendedcan accurately be achieved, while appropriately cooperating with otherdriving force controls.

Particularly, the basic target torque determinator 51 determines thebasic target torque based on the target acceleration determined by thevehicle speed control device of the following travel control device 60,etc. Since the final target torque determinator 55 determines the finaltarget torque based on the basic target torque and the torque reductionamount determined based on the operating state of the vehicle other thanaccelerator pedal operation, and the engine controller 59 controls theengine 10 so as to output the final target torque, the vehicle behaviorwhich the operator intended can accurately be achieved even when thevehicle speed control is performed by the following travel controldevice 60, etc.

It should be understood that the embodiments herein are illustrative andnot restrictive, since the scope of the invention is defined by theappended claims rather than by the description preceding them, and allchanges that fall within metes and bounds of the claims, or equivalenceof such metes and bounds thereof, are therefore intended to be embracedby the claims.

LIST OF REFERENCE CHARACTERS

-   1 Intake Passage-   5 Throttle Valve-   10 Engine-   13 Fuel Injector-   14 Ignition Plug-   18 Variable Intake Valve Mechanism-   25 Exhaust Passage-   30 Accelerator Opening Sensor-   39 Vehicle Speed Sensor-   50 PCM-   51 Basic Target Torque Determinator-   53 Torque Reduction Amount Determinator-   55 Final Target Torque Determinator-   57 Torque Change Filter-   59 Engine Controller-   60 Following Travel Control Device-   100 Engine System

What is claimed is:
 1. An engine control device for controlling anengine based on a plurality of operating states of a vehicle, the enginecontrol device comprising: a processor configured to execute softwareprograms stored in a non-volatile memory of the engine control device,said software programs including: a basic target engine torquedeterminator for setting a target acceleration of the vehicle based on afirst operating state of the vehicle, said first operating state of thevehicle being defined by an accelerator pedal operation, and determininga basic target engine torque based on the target acceleration of thevehicle; an actual engine torque reduction demand determinator fordetermining an existence of a demand to reduce an actual engine torquebased on a second operating state of the vehicle, said second operatingstate of the vehicle being defined by a steering wheel operation; anactual engine torque reduction amount determinator for determining anactual engine torque reduction amount when the demand to reduce theactual engine torque is determined to exist, the determined actualengine torque reduction amount being based at least in part on acalculated steering speed; a final target engine torque determinator fordetermining a final target engine torque, wherein the determined finaltarget engine torque is obtained by subtracting the determined actualengine torque reduction amount from the determined basic target enginetorque; and an engine controller for adjusting at least one of athrottle valve position, a fuel injection amount and a fuel injectiontiming of a fuel injector, an ignition timing of an ignition plug, andopen-close timings of an intake valve and an exhaust valve such that theactual engine torque is reduced so as to output the determined finaltarget engine torque.
 2. The engine control device of claim 1, furthercomprising a following travel control device for controlling a travelingspeed of the vehicle by performing a following travel control, thefollowing travel control including detecting a distance between thevehicle and a preceding vehicle via a radar, and setting the targetacceleration of the of the vehicle such that the distance between thevehicle and the preceding vehicle is kept constant, wherein when thedemand to reduce the actual engine torque is determined to exist, evenduring the performing of the following travel control, the final targetengine torque determinator still determines the final target enginetorque by subtracting the determined actual engine torque reductionamount from the determined basic target engine torque.
 3. An enginecontrol device for controlling an engine based on a plurality ofoperating states of a vehicle, the engine control device comprising: aprocessor configured to execute software programs stored in anon-volatile memory of the engine control device, said software programsincluding: a basic target engine torque determinator for setting atarget acceleration of the vehicle based on a first operating state ofthe vehicle, said first operating state of the vehicle being defined byan accelerator pedal operation, and determining a basic target enginetorque based on the target acceleration of the vehicle; a change rateacquirer for acquiring a rate of change of a steering speed of thevehicle based on a second operating state of the vehicle, said secondoperating state of the vehicle being defined by a steering wheeloperation; a target additional deceleration setter for increasing atarget additional deceleration, the target additional deceleration beingdefined by a deceleration amount that is added to the vehicle accordingto the acquired rate of change of the steering speed of the vehicle, andwherein a rate of the increase of the target additional decelerationlessens as the rate of change of the steering speed of the vehicleincreases; an actual engine torque reduction amount determinator fordetermining an actual engine torque reduction amount according to thetarget additional deceleration when an actual engine torque reductiondemand is determined to exist; a final target engine torque determinatorfor determining a final target engine torque, wherein the determinedfinal target engine torque is obtained by subtracting the determinedactual engine torque reduction amount from the determined basic targetengine torque; and an engine controller for adjusting at least one of athrottle valve position, a fuel injection amount and a fuel injectiontiming of a fuel injector, an ignition timing of an ignition plug, andopen-close timings of an intake valve and an exhaust valve such that theactual engine torque is reduced so as to output the determined finaltarget engine torque.